Remote Measurement of Small Busbar Voltage

Remote busbar voltage can be accurately measured using capacitive voltage dividers, isolated ADC systems, or voltage drop methods with non-invasive probes.

Capacitive Voltage Divider Method

For A

C busbars, a capacitive voltage divider is commonly used to reduce the high busbar voltage to a measurable level without direct current flow. This involves placing a capacitor plate over an insulated busbar to form a first capacitor, with a second capacitor connected to ground to create a voltage divider. A voltage measurer then calculates the AC voltage based on the measured voltage at the capacitor plate, the known capacitances, and the frequency of the AC signal.

This method allows non-contact, remote measurement while minimizing leakage currents and maintaining safety.

Voltage Drop Measurement

For D

C busbars, a simple and widely used approach is to measure the voltage drop between two points on the busbar. Two probes are attached at a fixed distance, and the voltage difference is measured using a voltmeter or data logger. The busbar voltage can then be inferred using Ohm's Law, taking into account the conductor's resistance, cross-section, and temperature.

This method is practical for industrial applications like aluminium smelters and allows semi-permanent or portable measurement setups. Isolated ADC-Based MeasurementHigh-accuracy remote voltage measurement can also be achieved using isolated analog front-end (AFE) systems with delta-sigma ADCs. These systems scale the busbar voltage to the ADC input range using fixed-gain amplifiers and provide simultaneous multi-channel sampling.

Such designs allow integration with intelligent electronic devices (IEDs) or protection relays, enabling remote monitoring, fault detection, and data logging without direct electrical contact with the busbar.

Practical Considerations

Insulation and safety: Ensure proper insulation between the busbar and measurement device to prevent leakage or hazards. Temperature effects: Capacitor and conductor properties may vary with temperature, affecting measurement accuracy. Frequency and signal type: AC and DC busbars require different measurement approaches; capacitive dividers are suited for AC, while voltage drop or isolated ADCs are suitable for DC.

Integration with monitoring systems: Remote measurement systems can be connected to SCADA or data acquisition systems for continuous monitoring and analysis. By selecting the appropriate method—capacitive dividers for AC, voltage drop for DC, or isolated ADCs for high-accuracy applications—small busbar voltages can be measured remotely and safely with minimal interference to the system operation.